Ha....if U wanna have a color logo on metal, there are several way, 1. Silkscreen on metal with metal primer sparyed in the first place. 2. So called '滴膠' in watch manufacturing industry, they are liquidify enamel actually, just apply them on the metal indentation, then expose them under intense UV light to cure the enamel. U can see them on the top ring of some watches.
3. Add sticker, of course.
4. Apply an aluminum foil on the metal surface, the foil was printed with a logo of course.
There are so many ways la.